Markarian 273 is a galaxy merger, the result of two or more galaxies colliding. When observed in mid infrared, two nuclei are visible, with a projected separation of about 0.75 kiloparsec.[2] The southwest nucleus is known to be active, due its X-ray emission,[3] while the northeast nucleus too displays a heavily abosrbed X-ray spectrum, indicating that is also active.[2] The optical emission of the southwest nucleus corresponds to a type II Seyfert galaxy while the north one of a LINER.[4] A third component in the nuclear region is visible at the southeast in the radiowaves and could be a star cluster.[3]
The galaxy experiences a starburst, with a star formation rate of 139 M☉ per year.[5] This activity makes the galaxy shine bright in the infrared and it is categorised as ultra-luminous infrared galaxy, with total infrared luminosity of the galaxy is estimated to be 1012.1L☉.[6] The startburst takes place in a rotating disk with a radius 120 pc and a total mass of 2.6×109M☉ which surrounds the north nucleus.[7] It has been suggested that this is the location of compact luminous supernovae remnants and radio supernovae.[8] The startburst is fed by large amounts of cold molecular gas. The gas has complex kinematics due to the presence of outflows. A kiloparsec scale outflow is visible towards the north in CO imaging, with the flow rate of 600 M☉ per year.[5] The outflows reach about 5 kpc from the nucleus.[9] There is also evidence of a bipolar superbubble.[10]
The merger has a tidal tail extending southwards for 40 kiloparsecs, that is seen edge on.[3] Also south of the galaxy lies a giant X-ray nebula, measuring 40 by 40 kiloparsecs in size, that isn't closely related with the tidal tail. The gas temperature of the nebula is estimated to be 7 million K, possibly heated by galactic outflows.[2] Filaments and clumps of ionised gas visible in OIII are extending about 23 kpc to the east.[11] A warm gas ionised halo extends about 45 kpc from the nucleus, and is probably tidal debris from the merger.[12] When observed in radiowaves the galaxy has two large plumes, one to the south, extending to about 100 kpc, and one dimmer to the north, extending to about 190 kpc.[13]
^Rodríguez Zaurín, J.; Tadhunter, C. N.; Rupke, D. S. N.; Veilleux, S.; Spoon, H. W. W.; Chiaberge, M.; Ramos Almeida, C.; Batcheldor, D.; Sparks, W. B. (November 2014). "Extended warm gas in the ULIRG Mrk273: Galactic outflows and tidal debris". Astronomy & Astrophysics. 571: A57. arXiv:1407.6301. Bibcode:2014A&A...571A..57R. doi:10.1051/0004-6361/201423540. S2CID59132144.
^Spence, R. A. W.; Zaurín, J. Rodríguez; Tadhunter, C. N.; Rose, M.; Cabrera-Lavers, A.; Spoon, H.; Muñoz-Tuñón, C. (11 June 2016). "No evidence for large-scale outflows in the extended ionized halo of ULIRG Mrk273". Monthly Notices of the Royal Astronomical Society: Letters. 459 (1): L16–L20. arXiv:1603.00488. doi:10.1093/mnrasl/slw033.
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